Fix panel session matching for prefix-colliding paths

[TomCC7]

Summary

• validate OpenCode session records against the exact requested directory
• correlate status entries with the validated session IDs before panel selection
• apply the same exact-directory check during direct session discovery
• add regressions for cc/frontier and cc/frontier_/abc

Root cause

The client treated OpenCode directory filters as exact. Prefix-style responses could therefore bind two panels with similar paths to the same session.

Verification

• cargo test
• cargo fmt -- --check
• cargo clippy --lib -- -D warnings